The present invention relates to a vibration testing apparatus and a vibration testing method for conducting hybrid vibration experiments on structures.
A method is described of conducting vibration experiment by using a shaking table, by numerically modeling a part of the structure while building up an actual model for the remaining parts thereof, for determining behavior of the structure when being subjected to an earthquake or the like, for example, in xe2x80x9cA hybrid vibration experiment with using a model of soil-foundation systemxe2x80x9d by KOBAYASHI and TAMURA, Articles of a first (1st) symposium relating to an improvement on protection against the earthquake disaster upon the basis of analysis of breaking process of structures, Mar. 27, 2000, issued by a technology propelling organization of civil engineering society, pp. 145-150. This method is based on the condition that concentrated load is applied onto a vibration point. However, with a structure that cannot be easily divided into numerical and actual models, the displacement is distributed, which is inherently ought to be given on the boarder between both of those models; therefore it is difficult to determine such displacement with high accuracy by using only a single vibrator.
For overcoming such a drawback, Japanese Patent Laying-Open No. Hei 8-292122 (1996) or Japanese Patent Laying-Open No. Hei 9-126942 (1997), for example, describe that deformation of a great degree of freedom is applied onto the model as a target of vibration with using a large number of the vibrators. For example, in the Japanese Patent Laying-Open No. Hei 8-292122 (1996), a plurality of vibrating or shaking tables of the same size are positioned, being separated by such a predetermined distance therebetween, such that each the shaking table can be moved in synchronism therewith and moved independently, and that each the shaking table can be moved while keeping the correlation therebetween, thereby enabling them to be used, also as a shaking table of a large-size.
Also, in the Japanese Patent Laying-Open No. Hei 9-126942 (1997), for enabling to give a plurality of vibrations having a phase difference therebetween, or those being different in the cycle thereof, both a sample and a second vibrating stage are received within a first vibrating stage, being formed in a box-like shape and opened at the upper surface thereof, in a vibration tester. The second vibrating stage takes counterforce to the first vibrating stage, thereby enabling vibrations different from that given from the first vibrating stage onto the sample disposed thereon.
Further, for the purpose of complementing the method of the first-mentioned document, in xe2x80x9cDynamic-response analysis of bridge by taking coupling of soil-foundation into considerationxe2x80x9d by TAKAHASHI, and others, Articles of a first (1st) symposium relating to an improvement on protection against the earthquake disaster upon the basis of analysis of breaking process of structures, Mar. 27, 2000, issued by a technology propelling organization of civil engineering society, pp. 151-156, a lumped mass model is used in the hybrid experiment, in which the structure is considered to be a non-linear element.
In what is described in the first-mentioned document, enabling the hybrid vibration experiments therewith, the numerical model and the actual model are divided on the boundary therebetween, ideally by a point. Accordingly, it is only possible to treat the general structure, which shows complex behaviors, in an approximate manner; therefore a modeling is desired that is closer to reality. Also, with those described in the Japanese Patent Laying-Open No. Hei 8-292122 (1996) and the Japanese Patent Laying-Open No. Hei 9-126942 (1997), though having an advantage that the sample can be vibrated at a plurality of points, however there is paid almost no consideration to how the bad influences should be reflected on the structure of the vibrator, in particular, when the vibration response of the structure greatly depends on the peripheral circumferences. For example, a load is applied from a soil onto a pile of the bridge, which is buried into the soil, and this load depends on the deformation of the pile. Also, the structure receives fluctuation pressure from winds, and this fluctuation pressure may be a factor of vibration generation. Thus, the fluctuation pressure is influenced by the deformation of the structure. Also the same phenomenon occurs within the structure in water.
Moreover, since the non-linear lumped mass model is used as the calculation model in the second-mentioned document, the accuracy of calculation can be improved; however, since it also tries to achieve the vibration displacement distribution of the actual model by using the single vibrator, therefore a further improvement is desired for the purpose of obtaining the actual displacement distribution with higher fidelity.
According to the present invention, being accomplished by taking the drawbacks of the conventional arts mentioned above into the consideration, an object is to make the so-called hybrid vibration experiment possible on the structure in a wide region thereof. Another object, according to the present invention, is to bring the method for vibration experiment to be executed accompanying with the shaking tests and numeral calculations to be applicable also onto the structure being difficult to be divided by the point and the structure receiving ill influences from the peripheral circumstances thereof. A still further object, according to the present invention, is to accomplish a hybrid vibration experimental apparatus, being applicable to structures widely, and also a vibration-response analysis apparatus for use therein. And, according to the present invention, it is an object to achieve one or more of those objects.
For accomplishing the objects mentioned above, according to the present invention, there is provided a vibration testing apparatus, for analyzing vibration response in a structure by using a computer, shaking a portion of the structure with using an actual model simulated thereto, while analyzing the vibration response of a numerical model simulated to remaining portions thereof The apparatus has a loading member neighboring the actual model; a plurality of vibrators for shaking the actual model through the loading member; and a control for the plurality of vibrators, wherein the control controls the plurality of vibrators, so that a load is applied onto the actual model causing distributed displacement thereupon.
Also, according to the present invention, in the vibration testing apparatus as described in the above, it is preferable that the control apparatus controls the plurality of vibrators upon the distributed displacement, which is memorized or stored in the computer in advance, and that a displacement detector is provided in each of the plurality of vibrators for detecting shaking displacements by the vibrators.
Further, according to the present invention, for accomplishing another object mentioned above, there is also provided a hybrid vibration testing apparatus having a deformation loading apparatus for deforming a sample; and a computer for calculating vibration response in a structure model, which is imaginarily connected to the sample, and for giving an instructing to the deformation loading device, thereby causing the deformation in the sample. The deformation loading device includes a loading member neighboring the sample and causing the deformation in the sample through deformation of itself; a plurality of vibrators for causing the deformation in the loading member, each being fixed at one end thereof; and counterforce measurement apparatuses, each for measuring the counterforce, which the sample gives to the loading apparatus. The computer calculates out the vibration response in a structure model by using a distributed counterforce value detected by the counterforce measurement apparatus and an external force applied onto the structure model. The vibration response is a vibration response having a greater degree of freedom than that of the vibrators, and the computer further instructs a displacement amount to each of the vibrators upon basis of the vibration response calculated out therein.
Also, in the hybrid vibration testing apparatus as described above, it is preferable that the computer instructs the displacement amount to each of said vibrators, so that the deformation caused in the loading member by shaking of the vibrators coincides with the deformation of the loading member, which is included in the vibration response calculated out through the structure model. It is also contemplated that the computer calculates out the displacement amount to be instructed to each of said vibrators, using a least squares method.
Also, it is preferable that that the counterforce measurement apparatus is built up with load sensors, each of which is provided between the loading member and the sample, respectively, and the computer obtains a distributed counterforce by interpolating outputs of those load sensors. Also, it may further comprises apparatus for executing at least one of storing, displaying and outputting of the vibration response calculated by the computer, during vibration experiment or after completion thereof.
Further, it is contemplated that the counterforce measurement apparatus is built up with load sensors, each of which is provided between the loading member and the sample, respectively, and a loading member structure model is loaded into the computer, which model describes a relationship of deformation amount with respect to the load on the loading member at a connecting point between the loading member and the vibrator.
Moreover, according to the present invention, for accomplishing one of the objects mentioned above, there is also provided a hybrid vibration testing method, for analyzing vibration response in the entire structure by using a computer, shaking a portion thereof with using an actual model simulated thereto, while analyzing the vibration response of a numerical model simulated to remaining portions thereof. The method involves calculating the vibration response of the numerical model at a time when at least one of external force and shaking force is applied onto the structure; and applying a load to cause the distributed displacement on a loading member, which is neighbors the actual model, by using a plurality of vibrators, upon the basis of vibration displacement at a neighboring portion to said actual model, which is obtained in the computer. And in the hybrid vibration testing method as described above, it is contemplated that the external force is considered to be an inertia caused due to earthquake, and the vibration responses obtained are considered seismic responses caused by seismic acceleration.
And also, according to the present invention, in the hybrid vibration testing method as described above, it is currently preferable that the distributed counterforce is obtained by memorizing a loading member structure model describing a relationship between the load and the deformation amount, at positions where the vibrators are connected, into the computer; calculating the counterforce generated in the loading member by the computer, using the deformation amount, which is applied by each of vibrators, and the loading member structure model; obtaining a difference in the load by subtracting the counterforce calculated by the computer from the load value detected by the load detector provided in each of the vibrators; and obtaining the distributed counterforce of an entire loading member which causes the distributed deformation from the load of the difference in each of the vibrators.